# Input deaf/broken, repair, RX2 usage

**URL:** <https://discourse.myriadrf.org/t/input-deaf-broken-repair-rx2-usage/1006>\
**Category:** LimeSDR\
**Created:** [25 March 2017 14:24 UTC](https://discourse.myriadrf.org/t/input-deaf-broken-repair-rx2-usage/1006 "2017-03-25T14:24:11Z")\
**Posts on this page:** 9\
**Page:** 1

<div class="post-metadata">

**Author:** ![Ismas](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/ismas/32/718_2.png) [@Ismas](https://discourse.myriadrf.org/u/Ismas)\
**Post date:** [25 March 2017 14:24 UTC](https://discourse.myriadrf.org/t/input-deaf-broken-repair-rx2-usage/1006/1 "2017-03-25T14:24:11Z")

</div>

Hi there.

After two weeks of happy use my Lime seems broken. While adjusting receiving antenna, using a VOLMET signal on air VHF band as reference on SDR-Console, my RX1\_L went totally deaf. Confirmed with Gqrx and GRC. \_W and \_H works, but \_W shows a -15dB difference without the fix.  
Scenary: EasyFix 1 applied, gains LNA -15, TIA -12, PGA 4, passive BFM notch filter. Lime sitting in his isolated metal case. Maybe a static discharge, I don’t know.

I tried to select RX2 on GRC using the 2 channels trick but didn’t work for me  
File “/home/ismael/hw/LimeSDR/top\_block.py”, line 65, in **init**  
self.osmosdr\_source\_0 = osmosdr.source( args=“numchan=” + str(2) + " " + ‘driver=lime,soapy=0’ )  
File “/usr/lib/python2.7/dist-packages/osmosdr/osmosdr\_swig.py”, line 1173, in make  
return \_osmosdr\_swig.source\_make(\*args, \*\*kwargs)  
RuntimeError: Wrong device arguments specified. Missing nchan?

So, I have several question and pleas:

1. Is there any other thing I can check?
2. In the worst case, is it possible to send it back to Lime Microsystems for repair? I fear that it will imply replacing LMS7000
3. Could friends @csete, @SimonG4ELI and Myriad people update libraries and soft for selecting channel 2 inputs?

This is a big deal for me because had plans on decoding wide digital signals and experiment with osmo\* and DVB.

Regards

---

<div class="post-metadata">

**Author:** ![Ismas](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/ismas/32/718_2.png) [@Ismas](https://discourse.myriadrf.org/u/Ismas)\
**Post date:** [29 March 2017 11:25 UTC](https://discourse.myriadrf.org/t/input-deaf-broken-repair-rx2-usage/1006/2 "2017-03-29T11:25:28Z")

</div>

A follow-up on the subject.  
My RX1\_L seems not totally broken, as it receives signal but about -35dBm lower. It seems not shorted nor opened, but deafened. RXLNAL should have blown. RXMIX, RXTIA and the rest modules works normally on that band. So it’s not totally lost as an external LNA could still be used.

I’ve checked all possible polarization values in LimeSuite RBB tab for RXLNA awakening to no avail.

Also I’ve reviewed the event and I think it happened when RX1\_L got shorted for about 250ms when unproperly disconnected while LimeSDR was energized.

I wonder if Easyfix shunt coil removal leaves input less protected from unwanted spikes. i think it should be investigated.

I’d also like to hear from people with similar issue to share thoughs,

Regards.

---

<div class="post-metadata">

**Author:** ![Zack](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/zack/32/89_2.png) [@Zack](https://discourse.myriadrf.org/u/Zack)\
**Post date:** [29 March 2017 11:45 UTC](https://discourse.myriadrf.org/t/input-deaf-broken-repair-rx2-usage/1006/3 "2017-03-29T11:45:05Z")

</div>

Hello @Ismas,

Could you check please if transformer/balun is not physically broken on channel RX1\_L. Or share a good resolution picture of LimeSDR-USB RF RX1\_L part.

---

<div class="post-metadata">

**Author:** ![Ismas](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/ismas/32/718_2.png) [@Ismas](https://discourse.myriadrf.org/u/Ismas)\
**Post date:** [29 March 2017 20:45 UTC](https://discourse.myriadrf.org/t/input-deaf-broken-repair-rx2-usage/1006/4 "2017-03-29T20:45:44Z")

</div>

Thanks Zack,  
Apart of a small scratch It seems ok to me.

 ![](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/1X/0f4bc706150b7b380bf773a28d2ced014996f3f4.jpg)

Other view

 ![](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/1X/d122d912dddbe826b041562a646d4278e6abe940.jpg)

LNA adjust works on RX1\_L, only -35dB muffled

---

<div class="post-metadata">

**Author:** ![Ancer](https://avatars.discourse-cdn.com/v4/letter/a/278dde/32.png) [@Ancer](https://discourse.myriadrf.org/u/Ancer)\
**Post date:** [29 March 2017 22:23 UTC](https://discourse.myriadrf.org/t/input-deaf-broken-repair-rx2-usage/1006/5 "2017-03-29T22:23:47Z")

</div>

Mine version 1.4 im looking in your picture you missing T3 coil not sure with other limesdr.

---

<div class="post-metadata">

**Author:** ![Ismas](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/ismas/32/718_2.png) [@Ismas](https://discourse.myriadrf.org/u/Ismas)\
**Post date:** [30 March 2017 07:04 UTC](https://discourse.myriadrf.org/t/input-deaf-broken-repair-rx2-usage/1006/6 "2017-03-30T07:04:20Z")

</div>

Hi Ancer

T3 coil was removed to enhance reception under ~150Mhz. It’s a procedure documented on this list and wiki.

---

<div class="post-metadata">

**Author:** ![Ancer](https://avatars.discourse-cdn.com/v4/letter/a/278dde/32.png) [@Ancer](https://discourse.myriadrf.org/u/Ancer)\
**Post date:** [30 March 2017 11:58 UTC](https://discourse.myriadrf.org/t/input-deaf-broken-repair-rx2-usage/1006/7 "2017-03-30T11:58:08Z")

</div>

Try inject a signal on each pin of RX1\_L to see if receive part is actually damage basically tracing them until you reach the input of the chip.

---

<div class="post-metadata">

**Author:** ![Ismas](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/ismas/32/718_2.png) [@Ismas](https://discourse.myriadrf.org/u/Ismas)\
**Post date:** [1 April 2017 13:18 UTC](https://discourse.myriadrf.org/t/input-deaf-broken-repair-rx2-usage/1006/8 "2017-04-01T13:18:59Z")

</div>

Tested, no luck.  
Followed all track from input to chip, no difference in signal amplitude. Passive components seem OK, unless transformer coil is shorted. Don’t know how to check that without desoldering. Impedance curve variation?

Setup: Using TX1 as signal generator, all TXPAD and RXLNA, MIX, TIA and PGA gains minimum. Out-of-band sonde as atenuator.

 ![](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/1X/1d9d43e174dc6c13d14c66f980507781d678f2b5.jpg) 

This is deaf LNA1\_L vs unmoddifed LNA1\_W sensibility comparison on SDR Console:

 ![](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/1X/9b173030e4041beb326335d55d927bef304ea501.PNG) ![](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/1X/0a114a5d282020daf002352a20efb766fd31cb3e.PNG)

New ideas are always welcome.

---

<div class="post-metadata">

**Author:** ![Ancer](https://avatars.discourse-cdn.com/v4/letter/a/278dde/32.png) [@Ancer](https://discourse.myriadrf.org/u/Ancer)\
**Post date:** [1 April 2017 13:22 UTC](https://discourse.myriadrf.org/t/input-deaf-broken-repair-rx2-usage/1006/9 "2017-04-01T13:22:47Z")

</div>

You can try check the x-former for short pri to sec.